Indication of glacially-induced fault reactivation in Latvia, Lithuania and the Kaliningrad District of Russia from models of glacial isostatic adjustment

2020 ◽  
Author(s):  
Holger Steffen ◽  
Rebekka Steffen ◽  
Lev Tarasov
Keyword(s):  
Fault Reactivation ◽  
Glacial Isostatic Adjustment ◽  
Deformation Structures ◽  
Isostatic Adjustment ◽  
Stress Changes ◽  
Coulomb Failure ◽  
Sediment Deformation ◽  
Eastern Edge ◽  
Weichselian Glaciation ◽  
Unstable States

<p>We model the change of Coulomb Failure Stress (δCFS) during the Weichselian glaciation up until today at 12 locations in Latvia, Lithuania and Russia that are characterised by soft-sediment deformation structures (SSDS). If interpreted as seismites, these SSDS may point to glacially-induced fault reactivation. The δCFS suggests a high potential of such reactivation when it reaches the instability zone. We show that δCFS at all 12 locations reached this zone several times in the last 120,000 years. Most notably, all locations exhibit the possibility of reactivation after ca. 15 ka BP until today. Another time of possible activity likely happened after the Saalian glaciation until ca. 96 ka BP. In addition, some models suggest unstable states after 96 ka BP until ca. 28 ka BP at selected locations but with much lower positive δCFS values than during the other two periods. For the Valmiera and Rakuti seismites in Latvia, we can suggest a glacially-induced origin, whereas we cannot exactly match the timing at Rakuti. Given the (preliminary) dating of SSDS at some locations, at Dyburiai and Ryadino our modelling supports the interpretation of glacially-induced fault reactivation, while at Slinkis, Kumečiai and Liciškėnai they likely exclude such a source. Overall, the mutual benefit of geological and modelling investigations is demonstrated. This helps in identifying glacially-induced fault reactivation at the south-eastern edge of the Weichselian glaciation and in improving models of glacial isostatic adjustment.</p><p>This work has been published in Steffen et al. (2019).</p><p>Reference:</p><p>Steffen, H., Steffen R., Tarasov L. 2019. Modelling of glacially-induced stress changes in Latvia, Lithuania and the Kaliningrad District of Russia. Baltica, 32 (1), 78–90.</p>

scholarly journals Modelling of glacially-induced stress changes in Latvia, Lithuania and the Kaliningrad District of Russia

Baltica ◽  
2019 ◽  
Vol 32 (1) ◽  
pp. 78-90
Author(s):  
Holger Steffen ◽  
Rebekka Steffen ◽  
Lev Tarasov
Keyword(s):  
Fault Reactivation ◽  
Glacial Isostatic Adjustment ◽  
Deformation Structures ◽  
Isostatic Adjustment ◽  
Stress Changes ◽  
Coulomb Failure ◽  
Sediment Deformation ◽  
Eastern Edge ◽  
Weichselian Glaciation ◽  
Unstable States

We model the change of Coulomb Failure Stress (δCFS) during the Weichselian glaciation up until today at 12 locations in Latvia, Lithuania and Russia that are characterised by soft-sediment deformation structures (SSDS). If interpreted as seismites, these SSDS may point to glacially-induced fault reactivation. The δCFS suggests a high potential of such reactivation when it reaches the instability zone. We show that δCFS at all 12 locations reached this zone several times in the last 120,000 years. Most notably, all locations exhibit the possibility of reactivation after ca. 15 ka BP until today. Another time of possible activity likely happened after the Saalian glaciation until ca. 96 ka BP. In addition, some models suggest unstable states after 96 ka BP until ca. 28 ka BP at selected locations but with much lower positive δCFS values than during the other two periods. For the Valmiera and Rakuti seismites in Latvia, we can suggest a glacially-induced origin, whereas we cannot exactly match the timing at Rakuti. Given the (preliminary) dating of SSDS at some locations, at Dyburiai and Ryadino our modelling supports the interpretation of glacially-induced fault reactivation, while at Slinkis, Kumečiai and Liciškėnai they likely exclude such a source. Overall, the mutual benefit of geological and modelling investigations is demonstrated. This helps in identifying glacially-induced fault reactivation at the south-eastern edge of the Weichselian glaciation and in improving models of glacial isostatic adjustment.

scholarly journals Comparison of the glacial isostatic adjustment behaviour in glacially induced fault models

2016 ◽  
Author(s):  
Rebekka Steffen ◽  
Holger Steffen ◽  
Patrick Wu
Keyword(s):  
Fault Reactivation ◽  
Field Pattern ◽  
Lithostatic Pressure ◽  
Earth Model ◽  
Glacial Isostatic Adjustment ◽  
Spatial And Temporal Scales ◽  
Elastic Foundations ◽  
Isostatic Adjustment ◽  
Error Bar ◽  
Stress Changes

Abstract. We compare the glacial isostatic adjustment (GIA) behaviour of two approaches developed to model the movement of a glacially induced fault (GIF) as a consequence of stress changes in the Earth's crust caused by the GIA process. GIFs were most likely, but not exclusively reactivated at the end of the last glaciation. Their modelling is complicated as the GIA process involves different spatial and temporal scales and they have to be combined to describe the fault reactivation process accurately. Model approaches have been introduced by Hetzel & Hampel (2005, termed HA in this paper) and Steffen et al. (2014a, termed WU in this paper). These two approaches differ in their geometry, their boundary conditions and the implementation of stress changes. While the WU model is based on GIA models and thus includes the whole mantle down to the core-mantle boundary at a depth of 2891 km, the HA models include only the lithosphere (mostly 100 km) and simulate the mantle using dashpots. They further apply elastic foundations and a lithostatic pressure at the base of the lithosphere, while the WU models apply elastic foundations at all horizontal boundaries in the model with density contrasts. Using a synthetic ice model as well as the Fennoscandian Ice Sheet, we find large discrepancies in modelled displacement, velocity and stress between these approaches. The HA model has difficulties in explaining relative sea level curves in Fennoscandia such as the one of Ångermanland (Sweden), where differences of up to 118 m to the data (with data error of 18.7 m) result. The WU model differs by up to 11 m, but falls within the error bar of 11.6 m. In addition, the HA model cannot predict the typical velocity field pattern in Fennoscandia. As we also find prominent differences in stress, we conclude that the simulation of the mantle using dashpots is not recommended for modelling the GIA process. The earth model should consist of both lithosphere and mantle, in order to correctly model the displacement and stress changes during GIA. We emphasize that a thorough modelling of the GIA process is a prerequisite before conclusions on understanding GIF evolution can be drawn.

scholarly journals The sea cliff at Dwasieden: soft-sediment deformation structures triggered by glacial isostatic adjustment in front of the advancing Scandinavian Ice Sheet

2019 ◽  
Vol 2 ◽  
pp. 61-67 ◽  
Author(s):  
Małgorzata Pisarska-Jamroży ◽  
Szymon Belzyt ◽  
Andreas Börner ◽  
Gösta Hoffmann ◽  
Heiko Hüneke ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Structural Features ◽  
Soft Sediment ◽  
Deformation Structures ◽  
Isostatic Adjustment ◽  
Scandinavian Ice Sheet ◽  
Sediment Deformation ◽  
Soft Sediment Deformation ◽  
Sea Cliff ◽  
The Last Glacial

Abstract. Isostatic response of the Earth's crust as a consequence of the fluctuating extent of ice-sheet masses was accompanied by earthquakes probably due to local reactivation of pre-existing faults. Our study of a glacilacustrine and glacifluvial succession exposed on Rügen Island (SW Baltic Sea) indicates that some of the soft-sediment deformation structures within the succession must have formed shortly before the front of the Pleistocene Scandinavian Ice Sheet reached the study area (during the Last Glacial Maximum), thus during a stage of ice advance. Based on analysis of the textural and structural features of the soft-sediment deformation structures, the deformed layers under investigation are interpreted as seismites which formed as a result of seismically induced liquefaction and fluidisation.

Evidence of paleoseismic activity recorded in glaciolacustrine sediments predating the Weichselian glacial maximum in East Lithuania

2021 ◽  
pp. 1-15
Author(s):  
Jonas Satkūnas ◽  
Saulius Šliaupa
Keyword(s):  
Seismic Activity ◽  
Silty Sand ◽  
Soft Sediment ◽  
Northern Flank ◽  
Deformation Structures ◽  
Depth Difference ◽  
Sediment Deformation ◽  
Weichselian Glaciation ◽  
Southern Flank ◽  
Hypocenter Depth

Abstract Soft-sediment deformation structures (SSDS) were identified in proglacial lacustrine (glaciolacustrine) sediments dated to 25–24 ka in the Buivydžiai outcrop, situated 30 km north of Vilnius in east Lithuania. These sediments accumulated in front of the last Weichselian glaciation maximum. The SSDS originated due to sandy silt liquefaction that disrupted the decimeter-thick silty sand interlayer. A NW-SE trending Buivydžiai fault was mapped in the proximity (8 km) of the Buivydžiai outcrop. The fault is well traced by a dense drilling in the sediments of the preglacial Daumantai Formation in the basal part of the Quaternary cover and attributed to the earliest Pleistocene. Depth difference of the formation along the fault is ~5–8 m; the northern flank is relatively uplifted with respect to the southern flank. The Buivydžiai earthquake was most likely induced by formation of an elastic forebulge flexure of the Earth's crust in front of the ice sheet. The magnitude was evaluated ~M = 6.0–6.5 and was most likely of shallow hypocenter depth. Furthermore, the Bystritsa (Belarus) earthquake of magnitude M = 3.5–4.0 was registered in December 1908 to the east (12 km) of the Buivydžiai outcrop along the Buivydžiai fault, which points to recurrent seismic activity of this fault.

scholarly journals Postglacial strain rate – stress paradox, example of the Western Alps active faults

2021 ◽  
Author(s):  
Juliette Grosset ◽  
Stéphane Mazzotti ◽  
Philippe Vernant
Keyword(s):  
Strain Rate ◽  
Active Faults ◽  
Western Alps ◽  
Fault Reactivation ◽  
Deformation Pattern ◽  
Isostatic Adjustment ◽  
Flexural Response ◽  
Coulomb Failure ◽  
Direct Corollary ◽  
Gnss Data

Abstract. The understanding of the origins of seismicity in intraplate regions is crucial to better characterize seismic hazards. In formerly glaciated regions such as Fennoscandia North America or the Western Alps, stress perturbations from Glacial Isostatic Adjustment (GIA) have been proposed as a major cause of large earthquakes. In this study, we focus on the Western Alps case using numerical modeling of lithosphere response to the Last Glacial Maximum icecap. We show that the flexural response to GIA induces present-day stress perturbations of ca. 1–2 MPa, associated with horizontal extension rates up to ca. 2.5 × 10−9 yr−1. The latter is in good agreement with extension rates of ca. 2 × 10−9 yr−1 derived from high-resolution geodetic (GNSS) data and with the overall seismicity deformation pattern. In the majority of simulations, stress perturbations induced by GIA promote fault reactivation in the internal massifs and in the foreland regions (i.e., positive Coulomb Failure Stress perturbation), but with predicted rakes systematically incompatible with those from earthquake focal mechanisms. Thus, although GIA explains a major part of the GNSS strain rates, it tends to inhibit the observed seismicity in the Western Alps. A direct corollary of this result is that, in cases of significant GIA effect, GNSS strain rate measurements cannot be directly integrated in seismic hazard computations, but instead require detailed modeling of the GIA transient impact.

Strike-slip fault reactivation in the Western Alps due to Glacial Isostatic Adjustment

2020 ◽  
Author(s):  
Juliette Grosset ◽  
Stéphane Mazzotti ◽  
Philippe Vernant ◽  
Jean Chéry ◽  
Kevin Manchuel
Keyword(s):  
Slip Rate ◽  
Western Alps ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Fault Reactivation ◽  
Maximum Effect ◽  
Glacial Isostatic Adjustment ◽  
Fault Systems ◽  
Isostatic Adjustment ◽  
The Impact

<p>The Western Alps represent the zone of highest seismicity density in metropolitan France. The seismicity is mainly located along two NE-SW strike-slip fault systems: the right-lateral Belledonne Fault and the left-lateral Durance Fault. Glacial Isostatic Adjustment (GIA) is one of the most common processes given to explain intraplate seismicity (e.g., Scandinavia, North America) and is also proposed as a cause of present-day deformation in the Alps. In order to test the impact of deglaciation from the Last Glacial Maximum on pre-existing vertical strike-slip faults in the Western Alps (Belledonne and Durance Faults), we use a finite-element approach to model fault reactivation throughout the deglaciation period, from ca. 18 kyr up to today. The models are tuned to fit present-day deformation rates observed by geodesy (uplift rate up to 2 mm/yr and horizontal radial extension). Simplified models (homogeneous icecap and Earth rheology) show that, under optimum conditions, GIA stress perturbations can activate a NE-SW right-lateral strike-slip fault such as the Belledonne Fault, requiring the fault to have been pre-stressed up to near-failure equilibrium before the onset of deglaciation. The maximum effect of GIA is 1.7 meters of right-lateral slip over 20 kyr, with a peak of displacement between 20 and 10 ka. These models indicate that GIA can result in a maximum slip rate of 0.08 mm/yr averaged over the Holocene, in association with earthquakes up to Mw = 7 (if all displacement is taken in one event). These results are consistent with local paleoseismicity and geomorphology evidence on the Durance fault. However, the impact of GIA on the left-lateral Belledonne Fault is poorly constrained by these simple models. Additional models based on realistic Alpine icecap reconstructions and regional rheology structures will also be presented, that allow us to test the specific effects of GIA on Holocene deformation along both the Belledone and Durance Fault systems.</p>

3D soft-sediment deformation structures: evidence for Quaternary seismicity in the Madrid basin, Spain

Terra Nova ◽  
1997 ◽  
Vol 9 (5) ◽  
pp. 208-212 ◽  
Author(s):  
P.G. Silva ◽  
J.C. Canaveras ◽  
S. Sanchez-Moral ◽  
J. Lario ◽  
E. Sanz
Keyword(s):  
Soft Sediment ◽  
Deformation Structures ◽  
Sediment Deformation ◽  
Soft Sediment Deformation

Dead Sea shoreline facies with seismically-induced soft-sediment deformation structures, Israel

2000 ◽  
Vol 49 (4) ◽  
pp. 197-214 ◽  
Author(s):  
Dan Bowman ◽  
Dorit Banet-Davidovich ◽  
Hendrik J. Bruins ◽  
Johannes Van der Plicht
Keyword(s):  
Dead Sea ◽  
Soft Sediment ◽  
Deformation Structures ◽  
Sediment Deformation ◽  
Soft Sediment Deformation
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